Method and apparatus for transmitting channel state information in wireless communication system

Abstract

A method for receiving channel state information (CSI) by a base station, includes transmitting configuration information indicating whether to use a 4 antenna ports codebook, wherein a first codebook index for a first precoding matrix indicator (PMI) and a second codebook index for a second PMI for a specific CSI report mode with 4 antenna ports are determined when the UE is configured to use the 4 antenna ports codebook; and receiving the CSI indicating the first codebook index and the second codebook index, wherein a value of the first codebook index is determined as follows: when a rank indicator (RI) is 1, the value of the first codebook index is determined based on a value of the first PMI multiplied by 4, and when the RI is 2, the value of the first codebook index is determined based on the value of the first PMI multiplied by 4.

What is claimed is: 
     
       1. A method for receiving channel state information (CSI) by a base station in a wireless communication system, the method comprising:
 transmitting configuration information indicating whether to use a 4 antenna ports codebook, wherein a first codebook index for a first precoding matrix indicator (PMI) and a second codebook index for a second PMI for a specific CSI report mode with 4 antenna ports are determined when a user equipment (UE) is configured to use the 4 antenna ports codebook; and 
 receiving the CSI indicating the first codebook index and the second codebook index, 
 wherein a value of the first codebook index is determined as follows: 
 when a rank indicator (RI) is 1, the value of the first codebook index is determined based on a value of the first PMI multiplied by 4, 
 when the RI is 2, the value of the first codebook index is determined based on the value of the first PMI multiplied by 4, and 
 when the RI is 3 or 4, a precoding matrix corresponding to the first PMI is an identity matrix. 
 
     
     
       2. The method of  claim 1 , wherein a value of the second codebook index is determined as follows:
 when the RI is 1, the value of the second codebook index is determined as one of 0, 2, 8, and 10, 
 when the RI is 2, the value of the second codebook index is determined as one of 0, 1, 4, and 5, and 
 when the RI is 3 or 4, the value of the second codebook index is determined as one of integers from 0 to 1.5. 
 
     
     
       3. The method of  claim 1 , wherein, when the RI is 1 or 2, each of the value of the first PMI and the value of the second PMI is represented by 2 bits. 
     
     
       4. The method of  claim 1 , wherein a total payload size for indicating the first codebook index and the second codebook index is 4 bits. 
     
     
       5. The method of  claim 1 , wherein the specific CSI report mode is a specific submode of a periodic CSI report mode. 
     
     
       6. The method of  claim 1 , wherein when the RI is 1 or 2, a final precoding matrix is to be determined based on the first codebook index and the second codebook index. 
     
     
       7. The method of  claim 1 , wherein the CSI further includes a wideband channel quality indicator (CQI). 
     
     
       8. The method of  claim 7 , wherein the first codebook index, the second codebook index and the wideband CQI are reported in a same subframe. 
     
     
       9. The method of  claim 8 , wherein the RI is reported in a subframe different from the same subframe. 
     
     
       10. A base station for receiving channel state information (CSI) in a wireless communication system, the base station comprising:
 a transceiver; and 
 a processor operably coupled with the transceiver and configured to: 
 transmit configuration information indicating whether to use a 4 antenna ports codebook, wherein a first codebook index for a first precoding matrix indicator (PMI) and a second codebook index for a second PMI for a specific CSI report mode with 4 antenna ports are determined when a user equipment (UE) is configured to use the 4 antenna ports codebook; and 
 receive the CSI indicating the first codebook index and the second codebook index, 
 wherein a value of the first codebook index is determined as follows: 
 when a rank indicator (RI) is 1, the value of the first codebook index is determined based on a value of the first PMI multiplied by 4, 
 when the RI is 2, the value of the first codebook index has the value same as the value of the first PMI multiplied by 4, and 
 when the RI is 3 or 4, a precoding matrix corresponding to the first PMI is an identity matrix. 
 
     
     
       11. The base station of  claim 10 , wherein a value of the second codebook index is determined as follows:
 when the RI is 1, the value of the second codebook index is determined as one of 0, 2, 8 and 10, 
 when the RI is 2, the value of the second codebook index is determined as one of 0, 1, 4, and 5, and 
 when the RI is 3 or 4, the value of the second codebook index is determined as one of integers from 0 to 15. 
 
     
     
       12. The base station of  claim 10 , wherein, when the RI is 1 or 2, each of the value of the first PMI and the value of the second PMI is represented by 2 bits. 
     
     
       13. The base station of  claim 10 , wherein a total payload size for indicating the first codebook index and the second codebook index is 4 bits. 
     
     
       14. The base station of  claim 10 , wherein the specific CSI report mode is a specific submode of a periodic CSI report mode. 
     
     
       15. The base station of  claim 10 , wherein when the RI is 1 or 2, a final preceding matrix is to be determined based on the first codebook index and the second codebook index. 
     
     
       16. The base station of  claim 10 , wherein CSI further includes a wideband channel quality indicator (CQI). 
     
     
       17. The base station of  claim 16 , wherein the first codebook index, the second codebook index and the wideband CQI are reported in a same subframe. 
     
     
       18. The base station of  claim 17 , wherein the is reported in a subframe different from the same subframe.